[Buildroot] Using buildroot images (iso/ext2) in real target device (flash drive)

[Arnout Vandecappelle <arnout@mind.be>]

On Friday 27 April 2012 16:23:20 Willy wrote:
> So I've deleted the output/ folder, made some modifications and rebuilt 
> all obtaining a smaller kernel and a smaller fs.
> Now it boot, but always using the bzImage (I've only /boot/grub/* and 
> bzImage on my flash usb). 

 So where did the rest of your rootfs.ext2 go?  

> Every modifications does not survive to reboot.

 Maybe you changed the rootfs to an initramfs?


> So I've built the vmlinux image and tar fs, but I got
> "Grub Error 13: Invalid or unsupported executable format"

 vmlinux is not executable by grub, and a tar file is not readable
by the kernel.


 The proper approach is the following:

- Create a /boot/grub/menu.lst in your rootfs skeleton.

- Make sure you have the grub boot loader configured.

- Build kernel and rootfs.ext2.  Make sure BR2_LINUX_KERNEL_INSTALL_TARGET
is selected, so the kernel is inside the rootfs.ext2.  If you want extra
space in your rootfs to write files to it, set the 
BR2_TARGET_ROOTFS_EXT2_BLOCKS variable to the size of the root partition.
Note, though, that genext2fs creates that whole size in memory, so you
need to have enough RAM.

- Write rootfs.ext2 to the root partition: 'cat rootfs.ext2 > /dev/hdc1'

- Run 'grub --device-map=/dev/null --no-floppy' and give the following 
commands interactively:

device (hd0) /dev/hdc
root (hd0,0)
setup (hd0)
quit

This installs grub on /dev/hdc and makes it bootable.


 Regards,
 Arnout


-- 
Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
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